schoolswikiaorg-20200215-history
Levers
Levers are used to lift a weight or mass that would be too heavy to lift without a lot of force. The lever is one of the oldest Physics ideas that is still used today. Levers were used in Egypt to assist the Egyptians in erecting large obelisks. Levers reduce the amount of force that must be put into moving an object by increasing the distance, or achieve the opposite by reducing the distance and increasing the force. Lever Classes There are three different types of levers that exist whose methods of input and output vary. First-Class Levers The First-Class Lever is the most easily recognizable of the three. The most common, everyday example of a First-Class Lever is a see-saw. Scissors and pliers are also common examples of a First-Class Levers.A lever has many parts lever arm, fulcrum, effort and load. the fulcrum is where the lever pivots. A class 1 lever has the fulcrum in between the load and the effort. Second-Class Levers Class Two Levers are a bit different than Class One Levers. The fulcrum is on the far side and the effort that you exert is on the near side, meaning the load is in the middle. A bottle opener is a common example. You place the opener under the bottlecap (this is the fulcrum, or pivot point) and pull up, thus lifting off the load (the bottlecap). Note that you can push down on a Class Two Lever to achieve similar results. Staplers and nail clippers are common Class Two Levers that operate when pushed down upon. Third-Class Levers Class Three Levers are very similar to Class Two Levers, but the placement of the effort and load are switched. The fulcrum is still on the outside, but the load is on the other side, meaning that the effort is now in the middle. A baseball bat is a common example. The fulcrum would be your body, because your arms and the bat (they're connected in this example so we can treat them as one) pivot around it. The effort is exerted by your hands in an effort to move the load (the baseball) that is on the end of the lever (bat). A fishing rod, tweezers and tongs are all common examples of a class three lever. How To Remember A helpful way of remembering the classes of levers is with the mnemonic fle''x. ''f represents the f''ulcrum, ''l represents the l''oad, and ''e represents the ''effort. The order of the letters in '''fle'x reminds you which part of the lever is between the other two. So the first letter, f''', tells us that the ''f''ulcrum is between the load and effort in the first-class lever. The second letter, '''l, tells us that the l'oad is between the effort and the fulcrum for the ''second-class lever. Finally, the third letter, '''e, tells us that the 'e'ffort is between the load and fulcrum in the third-class lever. Levers Today Today, the role of large levers has been taken over by hydraulics and motors. Rather than finding the manpower to apply great force to one side of a lever in order to slowly lift, it is easier to use motors and pistons. Modern day solutions have the capabilities to lift a load straight up, which means that all of the effort that is put in lifts the weight higher up. The effort put into levers moved the load diagonally (up and towards the fulcrum), meaning that more effort had to be put in in order to raise the load the same height. However, as shown above, many everyday aiding objects are levers. In fact, parts of our bodies act as levers constantly (ie, bicep curls). Although levers have been surpassed for large projects, it seems that for the common person le *http://www.school-for-champions.com/science/machines.htm External Links *Cool java applet that demonstrates the principles of levers and torque. *Website that shows the different kinds of levers in action. *Shows how a trebuchet uses lever concepts. *A website] that quizzes you on the various types of levers. See if I taught you anything at all